1. Field of the Invention
The present invention relates to pumps, and particularly to submersible or barrel pumps which have a drive shaft mounted in a support housing connected at one end to a drive unit and at the other end to a rotor disposed in a rotor chamber which borders a lower bearing of the drive shaft and from which at least one lifting duct runs parallel to the support housing in the direction of the drive unit and an outlet for the pumped fluid.
2. Discussion of Related Art
In known submersible pumps the drive shaft is held in a coaxial support housing which is surrounded by an annular lifting duct. While liquid is being pumped, it is possible for some of the liquid to penetrate into the support housing past the lower shaft bearing. Thus, particularly in the case of high-speed pumps, there is the danger that the fluid will rise in the support housing as far as the drive unit or be thrown upwards and penetrate into the drive unit. Particularly in the case of aggressive fluids, this can lead to operational troubles and to the complete failure of the pump.
A known method of obviating this disadvantage is for the fluid which has penetrated into the support tube to be drained via a leakage opening which is situated at the upper end of the support housing. This method has, however, proved to be inadequate since, when the pump is stationary, the liquid in the support housing rises up to about the level of the liquid surrounding the pump and, when the pump starts up, the pressure suddenly becomes so great that the liquid in the support housing is flung up to the drive unit as if by an eruption.
A further disadvantage is that when the pump is lifted out of the fluid being pumped, the liquid in the support housing cannot drain without hindrance. Thus, when the pump has been removed, the liquid continues to drip out of the support housing for a lengthy period of time, which can lead to fouling and, particularly in the case of acids, to severe burning.